Method of making spark plugs



Aug.6,1929.' FORD 1,723,026

METHOD OF MAKING SPARK PLUGS Filed Oct. 1927 INVENTOR.

Patented Aug. 6, 1929.

HENRY FORD, OF DEARB GRN, MIGHTGAN:

METHOD OF MAKING SPARK PLUGS.

Application fild ember The object of'my' invention'is toprovide a spark plug of simple, durable, and inexpensive construction.

Still a further objectof mydnventionusto provide a spark plugwllerein-the porcelain may lie-extruded in the form of a bar from an extruding machine instead of being molded or cast and subsequently ground or machined in order to bring the porcelain to its final shape.

Still a further object of my invention is to provide a spark plug wherein the metal casing or shell thereof may be cast on to the spark plug in permanent molds whereby the said casing may be cast in its final form and nothing need be done after the casting except the thread thereon will have to be trued up and the electrode bent to proper shape.

Still a further object of my invention is to provide a spark plug wherein the metal casing may be cast directly on to the porcelain and the electrode wire may be placed in the mold so that the casing will be cast around this wire thereby providing means for holding the electrode wire into the casing accurately and insuring good electrical contact therewith.

With these and other objects in view my invention consists in the arrangement, construction, and combination of the various parts of my improved spark plug, as described in the specification, claimed in the claims, and illustrated in the accompanying drawings, in which:

Figure 1 shows a side elevation of a spark plug constructed in accordance with my in vention.

Figure 2 shows a vertical central sectional view of the spark plug illustrated in Figure 1.

Figure 3 shows a vertical central enlarged sectional view through the porcelain and the casing illustrating the bond between the easing and the porcelain.

Referring to the accompanying drawing I have used the reference number to indicate the porcelain of a spark plug. By referring to Figure 2 it will be noted that this porcelain is of cylindrical shape throughout its length, so that it may be formed by being extruded from an extruding machine in the form of a continuous bar, and then this bar may be cut to form blanks for porcelain. hen these blanks have seen so out, then the recess 11 may be formed in one end thereof 192'7. sea-m1 Ne. 2241096;

byan'y suitable means-and theelectrodewire 12 may beinseite'd therein; Thehole'for thiselectrode w'iremay' be either formed at thetimethat the'bar is extruded from the extruding machine, or it may bedrilled subsequently. The electrodewire is preferably fastened into the porcelainby' having an enlarged portion or shoulder 13 formed thereon by the upsetting process and then the upper end of the electrode wire is threaded as at 14 so that a nut 15 may be screwed down on the electrode to draw the shoulder 13 up against the bottom of the recess 11 to thereby lock the electrode into the porcelain and form a gas tight oint there-between.

hen the porcelain has been so formed, it is then placed in a suitable permanent mold having a recess therein wherein an electrode wire 16 has been inserted in such position that it will be properly placed when the shell 17 has been cast. The shell 17 is then cast by pouring molten metal into the mold to form the casing in the same manner castings have been made, in the past. The sur face of the porcelain which will come into contact with the molten metal, is preferably coated with a material 18 which will serve as a heat insulator, a cushion to protect the porcelain from the-molten iron, a gas seal, and a binder to hold the s )ark plug together. I have found flake grap lite very satisfactory for this purpose but do not desire to limit myself thereto.

The porcelain may be glazed at any suitable stage in the manufacture of the plug.

It willbe noted that when the casting is made, the molten metal will flow around the end of the electrode 16 which extends into the mold wherebythe metal will unite itself with the material of the electrode at least by surface cohesion so that the parts will be permanently united and a high electrical conductivity will be secured.

Among the many advantages resulting from the use of my improved spark plug, it should first be pointed out that the screw "iachine operations ordinarily necessary in connection with forming the shell are eliminated and the assembly of the spark plug is simplified. The proper positioning of the parts of the plug is also insured. A satisfactory bond between the electrode 16 and the shell is also insured without additional operations. The porcelain for this spark plug may be extruded from an extruding machine instead of being cast and then ground or machined to shape so that the forming of the porcelain is much cheaper and faster than in connection With other methods of forming porcelains With which I am familiar. The electrode is fastened into the porcelain and a gas tight joint is insured with a minimum of parts and operations.

Some changes may be made in the manufacture of my improved spark plug Without departing from the spirit of my invention, and it is my intention to cover by. my claims such changes as may be reasonably included within the scope thereof.

I claim as my invention:

1. The method of forming a spark plug consisting of forming the porcelain, coating the porcelain With a material adapted to initially form a heat insulator and cushion to protect the porcelain, from molten iron and to subsequently form a gas seal between the iron and porcelain and then casting an iron shell onto the porcelain.

2. The method of forming a spark plug consisting of forming the porcelain, coating the surface of the porcelain with flake graphite, and then casting an iron shell on the coated porcelain.

HENRY FORD. I 

